1. Field of the Invention
The present invention relates to a vehicular collision avoiding system for avoiding a collision with an obstacle located ahead of a vehicle, by braking the vehicle on the basis of the relative distance and the relative speed between the obstacle and the vehicle.
2. Description of the Prior Art
In the prior art, there is known a collision avoiding system for avoiding a collision with an obstacle, by detecting a forward obstacle with a radar carried on the vehicle, and by braking the vehicle automatically on the basis of the relative distance and the relative speed between the vehicle and the obstacle.
There is also known a steering assisting system for stabilizing the behavior of the vehicle against disturbances such as cross winds, by detecting the vehicular behavior from the yaw rate and the lateral acceleration of the vehicle, and by applying to the steering system, when the vehicle is disturbed by the cross winds or the like, a steering torque in a direction to suppress the change in the vehicular behavior through an actuator.
Here, when the collision avoiding system of the prior art performs substantial automatic braking on an uneven road having a high coefficient of friction, it may be difficult to change the running of the vehicle. As a result, a lateral force may be established in the tires to weaken the longitudinal force, thereby failing to establish a sufficient deceleration, or the radar may lose the obstacle, thereby failing to achieve a sufficient collision avoiding effect.
The present invention has been conceived in view of the background described above and has the object to enhance the collision avoiding effect, by stabilizing the vehicular behavior during automatic braking by the collision avoiding system.
In order to achieve the above-specified object, according to the present invention, there is provided a collision avoiding system for a vehicle, comprising: an obstacle detecting means for detecting an obstacle located ahead of the vehicle; a braking system for braking the vehicle; and brake control means for controlling the operation of the braking system on the basis of a relative distance and a relative speed between the vehicle and the obstacle, as detected by the obstacle detecting means. A steering system steers the vehicle, and steering controlling means outputs a steering command signal to control the operation of the steering system on the basis of a braking command signal outputted by the brake control means.
The influence of the disturbances from an uneven road or the like can be compensated for to effect collision avoiding control, by controlling the steering system according to the operation of the braking system, even if the vehicle is disturbed by an uneven road when the braking system is activated to avoid the collision with an obstacle.
In addition according to the present invention, the steering controlling means controls the operation of the steering system in a direction to suppress the influence of the disturbances and will influence the steering of the vehicle when the disturbances are generated. The collision avoiding control can thus be effected by controlling the steering system in the direction to suppress the influence of the disturbances.
Further according to the present invention, when the brake control means outputs the braking command signal, the steering controlling means corrects the steering command signal in a manner to substantially suppress the influence of the disturbances. Thus, the influence of the disturbances, which are liable to occur during braking, can be effectively suppressed because the influence of the disturbances is suppressed more substantially during braking of the vehicle than otherwise.
In addition according to the present invention, the steering controlling means corrects the steering command signal in accordance with the degree of the influence which is exerted upon the steering of the vehicle by the operation of the braking system. The operation of the steering system can thus be optimized by correcting the steering command signal to match the degree of the influence to be exerted upon the steering of the vehicle by the operation of the braking system.
Further according to the present invention, the degree of the influence exerted upon the steering of the vehicle by the operation of the steering system, is calculated on the basis of at least one of the road surface friction coefficient, the longitudinal acceleration of the vehicle, the braking force of the vehicle and the tie rod axial tension. It is thus possible to properly calculate the degree of the influence to be exerted upon the steering of the vehicle by the operation of the braking system.